During a public land mobile network (PLMN) search, a multi-radio access technology (multi-RAT) user equipment searches all of the RATs, e.g., Global System for Mobile Communications (GSM), Universal Mobile Telecommunications System (UMTS), and Long-Term Evolution (LTE), etc. Based on different search conditions and algorithms, the user equipment (UE) searches cells in a different RAT order. In the situation where two or more RATs share a common frequency band, a UE may attempt to synchronize with the incorrect RAT, thereby resulting in a delay in synchronizing with the correct RAT.
For example, the UE may search for a GSM RAT prior to searching for an LTE RAT. In the existing Third Generation partnership Project (3GPP) configuration, there is a common frequency band for GSM and LTE. The actual frequency band allocation of LTE and GSM within the common frequency band may vary from country to country. Since GSM and LTE operate on a common frequency band, there is a high possibility that a UE searching for GSM cells may detect LTE cells and try to synchronize with the LTE cell. In the event that the cell is not a GSM cell, the UE has wasted time synchronizing with an undesired RAT cell. As a result, the search time to synchronize with the desired RAT, in this example GSM, is lengthened.
Therefore, there remains a need in order to improve the RAT search time for a UE where there are two or more RATs on a common frequency band.